How to buy a STM?

Could you elaborate on the process of purchasing STM tokens? I'm a novice in the cryptocurrency realm and am seeking clarity on the steps involved. Specifically, where should I look to find a reliable exchange or platform that offers STM trading? Are there any specific prerequisites I need to fulfill, such as having a cryptocurrency wallet or meeting certain minimum deposit requirements? Additionally, are there any security measures I should take into consideration to ensure a safe transaction? Your insights would be greatly appreciated.